Project guidelines for construction of biodigesters in poor

Project guidelines for construction of biodigesters in poor
communities in Brasil
Lizelda Maria de Mendonça Souto
University of Pernambuco, Department of Civil Engineering, Recife (PE), Brazil
lmms_pec@poli.br
Viviany Nogueira
University of Pernambuco, Department of Civil Engineering, Recife (PE), Brazil
vivianynogueira@gmail.com
Emilia Kohlman-Rabbani
University of Pernambuco, Department of Civil Engineering, Recife (PE), Brazil
emilia.rabbani@upe.br
Ana Rita Drummond
University of Pernambuco, Department of Biofuels and Energy, Recife (PE), Brazil
annaritadrummond@gmail.com
Sergio Peres
University of Pernambuco, Department of Biofuels and Energy , Recife (PE), Brazil
sergperes@gmail.com
ABSTRACT:
goods and services without taking into account that this unbridled acquisition will lead to
an increase in the generation of solid waste that, in most cases, will not be properly
disposed of, culminating in the proliferation of vectors and causing incalculable damage to
the environment, to public health, to the population, and to the urban order. This study
presents projectual guidelines for sustainability of low income communities in urban
areas through the installation of biodigesters as an alternative for the proper disposal of
their organic solid waste and sewage in order to improve sanitation and enable the
generation of biogas and power for such communities. The guidelines were elaborated
based on interviews with community leaders, the socioeconomic profile of community
residents, the amount of waste generated, sewage drainage problems, availability of open
areas adequate for the installation of biodigesters, the post-installation maintenance
manual, as well as an analysis of the Brazilian laws and regulations that standardize the
construction aspects. The proposed guidelines are intended to assist managers in decision
making with regard to sanitation and generation of biogas from waste, which is currently a
problem for local development.
Keywords Sanitation, Biodigesters, Slums, Low income communities, Sustainability in
urban areas.
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1. INTRODUCTION
In large Brazilian cities, innumerable informal dwellings, also known as needy
communities, lack basic sanitation, safety, transportation, decent housing, and the means
to enable the development of infrastructure that could improve the quality of life for the
population. According to Fantinatti et al. (2015), informal dwellings arise spontaneously,
as in the cases of invasions or irregular settlement in difficult-to-access areas that are
established because of proximity to work or availability of open land. Faced with this
problem, the need to apply engineering knowledge in support of low-income communities
with projects that bring sanitation, leisure, education, sustainable housing, and generation
of energy to the population becomes evident.
In Brazil, basic sanitation is defined by Law 11.445/2007 as the set of services,
infrastructure, and operational installations for drinking water supply, sewage, street
cleaning, solid waste management, floodwater management, and urban drainage.
According to etymology, sanitation is the act or effect of sanitizing, disinfecting,
deodorizing; it refers to the application of measures to improve hygienic conditions of a
place or region, especially drainage, making it suitable for habitation and bringing
improvements to health. (Weiszflog, 2016).
Therefore, sanitation implies a determining factor and condition for public health, and
must be regarded as of interest to social policy for the protection of the population.
According to Embrapa (2010), 75% of hospital admissions in Brazil are associated with
the lack of basic sanitation, often related to informal housing combined with the absence
of three basic services: running water in at least one room, sewage network or septic tank,
and trash collection. (Observatório das Metrópolis, 2010)
Faced with these sanitation problems, the objective of this article is to bring alternatives
through project guidelines and a proposed layout for biodigesters, considering economic
viability and ease of installation and maintenance, that can be used to channel sewage and
solid waste in needy communities, improving the local basic sanitation and public health,
as well as contributing to the improvement of sewage spilled into bodies of water.
1.1 The city of Recife and basic sanitation
In middle- and upper-class neighborhoods of large Brazilian cities, it is not common for
the populace to stop and think about how many times they turn on faucets or the shower,
or flush the toilet. It is not a habit to analyze the consumption of water by families, the
neighborhood, the city, or the state where one lives, much less to think about the
collection, treatment, and maintenance of its sewer systems. (Revista Proteção, 2012).
According to the Municipal Sanitation Department of Recife (SANEAR), in the most recent
census conducted by the Brazilian Institute of Geography and Statistics, the city of Recife
had a population of approximately 1.5 million. Due to problems of extreme income
inequality, territorial settlement occurred through a series of invasions, occurring
especially in hazardous areas such as steep hillsides, floodplains, riverbanks, and along
canals. These areas are often surrounded by and constrained between central and upperpoverty
occupation adds up to a total of more than 500 favelas deprived of even the minimum of
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Sustainable Urban Communities towards a Nearly Zero Impact Built Environment
ISBN: 978-85-92631-00-0
Cidade do Recife, 2016a)
(Prefeitura da
The municipality of Recife covers 220 km²of area and is divided into six (6) Politicofor the purposes of forming, executing, and evaluating the
policies and plans of the government. Each RPA is subdivided into three(3)micro-regions,
which define local-level municipal interventions and coordination with the populace.
These micro-regions are subdivided into neighborhoods, and within them can be found
priority in urban recovery, land regularization, and social housing projects, including the
recuperation of degraded properties, the provision of social and cultural amenities, public
spaces, services, and locally(Fonseca et al., 2014, p.1).
The ZEIS were integrated in the City Master Plan in 2008. Today, Recife has 66 ZEIS
distributed throughout 94 neighborhoods. Such neighborhoods show symptoms of urban
land use exhaustion. Many of these neighborhoods are located in riparian áreas, near
drainage canals, or in sensitive hillside areas highly restrained from expanding and
installing urban infrastructure, resulting in a wide range of structural and socioenvironmental problems for their low-income residents, who have no other housing
options. (Secretaria da Cidade do Recife, 1997).
According to the National Basic Sanitation Plan (PLANSAB) 2013, the release of primary
sewage (human waste
feces and urine) and secondary sewage (other residential
wastewater) cannot be performed in places such as rudimentary pits (wells, excavation
holes), open ditches, drainage systems, storm sewers, rivers, lakes, or the sea without
proper treatment according to the parameters established by CONAMA Resolution 430 of
2011. However, the Brazilian reality is that 35% of the population (reaching over 60% in
Recife) relies on inadequate solutions for their sewage removal. Only20 million habitants
in Brazil have sewage disposal systems or septic tanks that are considered suitable for the
disposal of wastes. (Ministério das Cidades & Secretaria Nacional de Saneamento
Ambiental, 2014; Ministério das Cidades, 2014).
1.2 Use of biodigester systems in rural and urban areas
According to the United Nations Development Programme (PNUD) and the Ministry of the
Environment (MMA) (2010), a biodigesteris a closed chamber that provides appropriate
conditions for the fermentation of organic material carried out by methanogenic bacteria.
This decomposition process generates biogas, which is formed from the following gases in
these proportions: methane 50-70%, carbon dioxide 25-40%, hydrogen 1-3%, hydrogen
sulfide 0.1-0.5%, and other trace gases. The process of decomposition also produces
biofertilizers, which are effluents more suitable for being returned to bodies of water, and
which can be utilized in community gardens, community centers, and resident
associations.
fuel for a leprosy hosp
apud Balmant, 2009, p. 11). However, there are
reports that biodigesters may have been used for over 5000 years in countries such as
India and China. In Ghana, West Africa, interest in biogas began in the 1960s, but it was
only in the 1980s that this technology received greater attention from the government and
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universities, due to environmental problems. The use of biodigesters was strengthened by
the National Strategic Energy Plan, created to encourage the production of biogas in the
country, principally in kitchens of establishments, laboratories, hospitals, boarding
schools, barracks, among other institutions. (Richard et al., 2011).
In the study by Richard et al. (2011), the reutilization of wastewater generated by students
and workers at four universities in Ghana to generate biofertilizers and biogas was
analyzed. The total daily production of biogas at the four universities was 1,378.5 m³ and
291.3 m³ during the school year and on holiday, respectively. This biogas could help
reduce the amount of Liquefied Petroleum Gas (LPG) required by the university
restaurants or to reduce electricity costs. According to Santana et al. (2012), 1 m3 can
generate 1.43 kWh of electricity and is the equivalent of 0.45 kg of LPG. According to Peres
(2010), 1 m3of biogas with 60% methane has a calorific value of 19.52 MJ.m-3. The
advantages of treating waste in a biodigester are a reduction in the amount of waste, the
generation of a renewable energy source (biogas), and the production of effluent with little
odor and rich in nutrients that can be used in agriculture. According to Olugasa et al.
(2014), a study conducted in Nigeria revealed that biogas can be na alternative to
conventional energy sources with the added benefit to the environment of removing
pollutant substances from nature and transforming them into renewable energy.
The study made by Turdera and Yura (2015) in the city of Dourados in Mato Grosso do Sul,
Brazil, simulated the home use of biogas, where 8.93m³ of biogas per day was able to
provide for the cooking of meals, illumination of four light bulbs for three hours,
refrigerate food, and provide a hot bath for a family of five people.
Despite being a reality for many years in other countries of the world, the use of
biodigesters remains in its infancy in Brazilian urban areas. However, a few examples of
research and development can be seen at Brazilian universities (Pimentel et al., 2015). In
urban areas, specifically ZEIS where there is disorderly settlement and high population
density, large-scale projects are not applicable due to the absence of free space within the
communities, necessitating a new compact design that is simple to install, operate, and
maintain.
2. METHODOLOGY
Initially, a literature review was conducted on the political-administrative distribution,
neighborhoods, and ZEIS, as well as the sanitation infrastructure of the city of Recife.
Subsequently, a descriptive Field study was conducted through photographic registry and
informal interviews with community leaders in the ZEIS of Borborema, Vila
Arraes,andCarangueijoTabaireswith the goal of identifying, mapping, and observing the
flow of sewage and the disposal of Municipal Solid Waste (MSW), discovering the locations
of open areas for installation of biodigesters, tracing the socio-economic profile of
residents, and estimating the electrical current necessary to supply homes, residents
associations, or community centers open to all local residents.
Using the ESIG program, Geographic Information of Recife (Prefeitura da Cidade do Recife,
2016b), it was possible to visualize the proximity of the communities visited to bodies of
water, and to map rivers, drainage canals, lakes, basins, and the sea, as well as to store
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information necessary for a potential study of environmental impacts caused by improper
sewage disposal.
Project guidelines were proposed
based on laws and technical standards, international and national case studies in urban
and rural areas, technical manuals from biodigester manufacturers, a survey of the
average wastewater volume produced per family, and the Pernambuco Solid Waste State
Plan (PERS-PE), generating as output biofertilizers, water, and biogas that can be utilized
within the local community. The proposed guidelines also take into account the use of lowcost construction materials and the ease of installation and operation by the local
community residents.
3. EXPLORATORY STUDY IN A ZEIS OF RECIFE
The exploratory field visits were conducted in 2015 and 2016 at three ZEIS communities
in the Recife Metro Area: Borborema, Vila Arraes, and Carangueijo Tabaires. The visits
were performed to collect data for a pilot project biodigester proposal and note the
existing possibilities for the implantation of biodigesters in needy communities. In the
ZEIS of Borborema, a potential area for the biodigester installation was identified, capable
of attending the needs of a few homes and whose biogas could be channeled to community
centers.
CAD Software (Industrial design) was used, with boundaries provided by ESIG
(Geographic Information of Recife),to map the ZEIS and visualize their proximity to bodies
of water. With use of CAD tools, ESIG, and photographic records, it was possible to identify
the irregular and inadequate disposal of waste and sewage in the community of
Caranguejo Tabaiares, Figure1, and its interconnection with the Capibaribe River, with the
ABC drainage canal, and with the Nature Conservation Unit (NCU) Zeca Island.
Figure 1. Location of inadequate waste and sewage treatment in the visited ZEIS. Source: Created by
the author based on ESIG and photographic records.
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According to the informal interviews with local residents during the exploratory visits,
respiratory illnesses, meningitis, leptospirosis, hemorrhagic dengue, chikungunya, zika,
and scorpion bites have been reported and have been the cause of death for many children
in the poorest communities due to the unsanitary conditions to which they are subjected.
4. DEFINITION OF GUIDELINS FOR THE PREPARTION OF PROJECTS AND LAYOUT
PROPOSAL FOR URBAN BIODIGESTERS
The guidelines were divided into three sub-items: (1) basic elements, (2) choice of location
and minimum distances from areas of influence, and (3) specific elements to establish
criteria for the development of biodigester projects in needy communities. Based on
as on data obtained from the exploratory visits to needy areas of Recife, the criteria are
detailed on the following flowchart:
Figure 2. Guidelines for Project Preparation. Source: Created by the author based on Fortlev, 2016;
Fantinatti et al., 2015; Creder, 2006.
Table 1 shows the local legislation, resolutions, and technical standards relevant to the
creation of a proposed biodigester layout for needy areas in the city of Recife. Some of the
topics considered in the references, while relevant, did not generate guidelines because
they are practices and values already deeply ingrained in the culture of the technical
manuals of the researched biodigesters.
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Table 1.Legislation used to prepare the Recife biodigester projectnn
Legislation
Technical Manual no. 001 CPRH
Dimensioning for septic tanks and
complementary basic units
Law n. 16.113/1995 - Analysis of lots in
a ZEIS - Art. 9, 10, and 11
CONAMA Resolution no. 430/2011
Art. 21 - Effluent discharge
Art. 23 Ecotoxicity Test
Art. 25 Sample Collection
Art. 26 Laboratory Tests
CONAMA Resolution no.375/2006
NBR 7229/1993
Guidelines
Construction in open terrain, with minimum distances:
1.0 m from foundations, sub-soil garage walls, and underground
deposits;
1.0 m from constructions, land boundaries, sinks, swales, and local
water lines.
Minimum distances:
5.0 m from buried water reservoirs and swimming pools.
3.0 m from trees and any points of public water supply.
15 m from groundwater wells.
Maximum lot size of 250m2, able to be broken down into a
minimum area of 40m2and minimum lot of 18m2.
Art. 21 - Conditions for discharge of effluents, considering
parameters established for pH, BOD, COD, temperature, and
absence of floating materials.
Art. 23
Ecotoxicity test for effluent from sewage treatment
systems.
Art. 25
The sample collection and analysis of waste water
according to specific rules.
Art. 26 The laboratory tests must be performed by laboratories
accredited.
The biological sludge can be neutralized and used in agriculture as
a source of organic material and nutrients for plants.
Dimensioning of the tank used in conjunction with the biodigesters
and the sand filter for complementary treatment of liquid effluent
are based on the formulas for prismatic single-chamber septic pits
and sewage systems for buildings.
Based on the legislation applicable to biodigesters and the exploratory analysis in the field,
the Total Waste (RT) value was calculated in accordance with Equation (1), considering
the value of Organic Waste (RO) produced per person/day added to the waste water (NA)
generated per person/day.
The RO value (0.9924 kg/person/day) was calculated from the Pernambuco Solid Waste
State Plan (SMAS & ITEP, 2012), which considers a percentage of 63% of gravimetric
composition for organic waste produced daily from the total daily amount of waste
produced per resident of the city Recife, estimated as 1.58 kg/person/day. For toilet waste
water (AN), the value of 0.1 kg feces+urine/person/day was considered, according to NBR
7229/1993. The total waste feeding into the biodigester daily can be calculated by the
expression below:
RT
Pop. * [(RO (kg/person/day) + AN (kg/person/day))]
(1)
The dimensions of the system were calculated according to NBR 7229/1997, providing a
diameter for cylindrical tanks of 2.20 m, minimum internal width of 1.85m, length/width
ratio (min. 2:1, max. 4:1)and using equation (2) below, the usable volume (V) in liters for
the biodigester can be calculated, corresponding to the sum of the volumes destined to
digestion, decantation, and storage of the spume);
V = 1000 + N(C x T + K x Lf)
(2)
where V= usable volume, in liters; N = number of people or contribution units (cannot be
less than 5 people); C= sewage contribution, in liters/person. T = Detention time, in days;
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K= rate of sludge accumulation digested in days equivalent to the accumulation time of
fresh sludge; Lf= fresh sludge contribution, in liters/person x days, or in liters/unit x days.
Because the biodigester will be connected to the toilet, inputs to the biodigester beyond
the RT of 5,462 kg/Day calculated by Equation (1) must be considered: the amount of
water released by the flushing action of the toilet (6 liters per flush) multiplied by the
quantity of flushes (A), considering an average of 5 to 8 flushes per resident per day, and
by the number of residents, shown in Equation (3). From the analysis, a complementary
treatment of the liquid effluent through the use of a buried sand filter (ABNT, 1993) is
indicated, as shown in Figure 3 (f).
QA 6 * [(No.res * A)]
(3)
To create the Urban Biodigester prototype (Figure 3),materials available in the market
were considered and a family made up of five (5) residents was contemplated. The
prototype will use a 5000 L fiberglass box (to fit the estimated waste according to
Equation 2); 3.40 m2 of PVC canvas, shown in Figure 3 and indicated by the letter (a); 100
mm PVC pipes shown by the letter (b) to transmit waste water (AN), for the output of
biofertilizer (c), and for receiving organic wastes (d). To operate the biodigester, a slope
of 5% should be used for the waste water pipes. For the biogas output, the installation of a
a meter to measure the
biogas output (h).
A commercially available inspection/interconnection box must be installed and adapted
with an interior grid having a minimum diameter of 30 cm (Tigre, 2016), illustrated by the
letter (f) in Figure 3, before the input pipes to the biodigester in order to hold accidental
discards of non-biodegradable material in the toilet, such as wipes and plastic packaging
that can clog the system (Fortlev, 2016).
Figure 3. Proposal for prototype urban biodigester to be utilized in needy areas of Recife.
For the digester operation phase, operational guidelines should be structured and
presented by various means of communication, helping to educate the target population
on proper use of the system. They should also consider the protection of users during the
manipulation of organic wastes (grass, feces from pets, chickens, pigs, biomass in general)
e during the maintenance of the inspection/interconnection box. As biogas is subject to
high pressure can be extremely inflammable, because of its proximity to residences, it is
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also necessary to prepare an evacuation plan for the area and contingency measures in
situations of hazard and emergency. Also, CONAMA Resolutions no. 375/2006 and
no.430/2011 should be used in order to neutralize the sludge and evaluate the effluent
generated.
This system is expected to generate ½ bottle of LPG/month and 20 L of
biofertilizer/month, considering that the first withdrawal during the production period
should occur after approximately 30 days have passed.
5. CONCLUSIONS
Large Brazilian cities, just like cities in other developing countries, have suffered because
of the close link between lack of efficient public policies, unequal income distribution,
disorderly settlement, and environmental degradation, which threatenthe preservation of
remaining natural areas located in protected areas and compromise the quality of life of
the general population, and especially that of excluded communities.
The guidelines proposed here should be analyzed as a set of ideas that will need to
constantly evolve, in order to overcome problems such as the sanitation crisis that
humanity lives in. The projects must be integrated and multidisciplinary in order to
develop biodigester profiles that are suitable for the urban environment where they will
be located. The most appropriate solution is that with lowest cost that meets the criteria
for safety and efficiency in sewage treatment, taken into account local limitations, the soreplicated at any location throughout the country).
The implantation of urban biodigesters is consistent with Law 11.445/2007,contributing
to the management of sewage and solid wastes, by using them as fuel for the biodigester
itself. It is believed that, once implemented and properly maintained, biodigesters can help
improve the quality of water in cities, avoiding contamination of water bodies,
ameliorating the effects of flooding, and reducing the proliferation of the viruses
responsible for zika, chikungunya, and dengue, as well as generate biogas from solid
wastes, which is currently a problem for city managers responsible for basic local
sanitation.
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